MPAHOMEPAGE 

Molecular Physics  
MPA Homepage > Scientific Research > Research Groups > Molecular Physics 
Go to: Group Home 
Focus
Empirically derived Hund's rules of the prequantummechanics era predict the ordering of the energy levels possessing different spin and orbital angular momentum quantum numbers. They have proved to be almost universally valid for atoms, molecules, and quantum dots. Yet, despite of a long standing debate the search for their origin persists, primarily due to the lack of the precise knowledge of the electronic structure in different spin states. We explore the origin of the first Hund rule for a twodimensional model of Helike systems and that of twoelectron quantum dots. These models represent ideal systems providing a direct fundamental insight into the structure of the internal part of the fullycorrelated wave functions, allowing an unambiguous argument. An examination of their probability density distributions reveals indeed the existence of a region in the internal space where the singlet wave function has a smaller probability density than the corresponding triplet one. Due to the presence of this conjugate Fermi hole the singlet probability density has to migrate far away from the center of the oneelectron potential. This rationalizes the wellknown broader electron density distribution of the singlet state relative to the corresponding triplet. This key observation explains the singlettriplet energy gap.
Comments to: Geerd HF Diercksen ghd@mpagarching.mpg.de 